This application contains subject matter that relates to and incorporates by reference in their entirety, for any and all purposes, the following non-provisional applications:
Ultrasonic Surgical Blade and Instrument Having a Gain STEP, U.S. Pat. No. 7,163,548.
TISSUE PAD FOR USE WITH AN ULTRASONIC SURGICAL INSTRUMENT, Ser. No. 11/245,819, filed Oct. 7, 2005;
COMBINATION TISSUE PAD FOR USE WITH AN ULTRASONIC SURGICAL INSTRUMENT, Ser. No. 11/246,794, filed Oct. 7, 2005;
ACTUATION MECHANISM FOR USE WITH AN ULTRASONIC SURGICAL INSTRUMENT, Ser. No. 11/246,826, filed Oct. 7, 2005;
CLAMP MECHANISM FOR USE WITH AN ULTRASONIC SURGICAL INSTRUMENT, Ser. No. 11/246,264, filed Oct. 7, 2005;
FEEDBACK MECHANISM FOR USE WITH AN ULTRASONIC SURGICAL INSTRUMENT, Ser. No. 11/246,384, filed Oct. 7, 2005;
HANDLE ASSEMBLY HAVING HAND ACTIVATION FOR USE WITH AN ULTRASONIC SURGICAL INSTRUMENT, Ser. No. 11/246,330, filed Oct. 7, 2005;
ULTRASONIC SURGICAL SHEARS AND TISSUE PAD FOR SAME, Ser. No. 11/065,378, filed Feb. 24, 2005; and
HAND ACTIVATED ULTRASONIC INSTRUMENT, Ser. No. 10/869,351, filed Jun. 16, 2004.
Further, this application shares a common specification with the following U.S. patent applications filed contemporaneously herewith: TISSUE PAD FOR ULTRASONIC SURGICAL INSTRUMENT, Ser. No. 11/751,733; ULTRASONIC WAVEGUIDE AND BLADE, Ser. No. 11/751,737; and MECHANISM FOR ASSEMBLY OF ULTRASONIC INSTRUMENT, Ser. No. 11/751,741.
Ultrasonic surgical instruments are finding increasingly widespread applications in surgical procedures by virtue of the unique performance characteristics of such instruments. Depending upon specific instrument configurations and operational parameters, ultrasonic surgical instruments can provide substantially simultaneous cutting of tissue and hemostasis by coagulation, desirably minimizing patient trauma. The cutting action is typically effected by an end-effector or blade tip at the distal end of the instrument, which transmits ultrasonic energy to tissue brought into contact with the end-effector. Ultrasonic instruments of this nature can be configured for open surgical use, laparoscopic or endoscopic surgical procedures including robotic-assisted procedures.
Ultrasonic surgical instruments have been developed that include a clamp mechanism to press tissue against the blade of the end-effector in order to couple ultrasonic energy to the tissue of a patient. Such an arrangement (sometimes referred to as a clamp coagulator shears or an ultrasonic transactor) is disclosed in U.S. Pat. Nos. 5,322,055; 5,873,873 and 6,325,811, all of which are incorporated herein by reference. The surgeon activates the clamp arm to press the clamp pad against the blade by squeezing on the handgrip or handle.
Some current ultrasonic shears devices, however, have the tendency to create tissue tags. Tissue tags are the tissue that remains clamped in the jaw that is not transected after the majority of the tissue in the jaw has been transected and falls away. Tissue tags may result from insufficient end-effector or blade tip proximal loading and/or lower proximal blade activity. Surgeons may mitigate tissue tags either through the addition of vertical tension (i.e. putting tension on the tissue using the blade) or rearward traction on the device in order to move the untransected tissue to a more active portion of the blade to complete the cut.
Some current ultrasonic shears devices utilize tissue pads that close in parallel with the surface of the blade. This presents certain problems in terms of the pressure profile exerted on the tissue. As tissue is compressed between the jaw and the blade, the distal portion of the blade deflects under load more than the proximal portion of the blade. This deflection is created in part by the portion of the blade distal to the most distal node of the device. It is also partly created by the deflection of the waveguide or transmission rod proximal to the most distal node. Additionally, the fact that blade amplitude decreases moving proximal of the tip of the blade makes the situation worse since the amount of energy transferred to the tissue, even if the pressure was constant, is reduced.
Current tissue pad designs utilize PTFE material to contact the tissue and blade. Although these designs have been adequate, they tend to suffer from longevity issues since the pads tend to deteriorate over long surgical procedures. Additionally, newer designs of clamp coagulator shears increase blade amplitude and/or the loading of the pad against the tissue and blade and overwhelm the pad material, resulting in less than required tissue pad life. The pad material limits the amount of force that may be applied against the tissue and blade, which in turn limits the tissue thickness or vessel size that some current clamp coagulator shears may effectively cut and coagulate. Current composite pads may be difficult or expensive to manufacture.
Some current designs of clamp coagulator ultrasonic shears are limited in the length of the active blade available for use by surgeons due to inherent limitations in the effective transfer of mechanical motion along the longitudinal path of the blade from the transducer assembly. Although new blade geometry has mitigated some of these problems, longer active blade lengths, or blades that have more mass (created by larger diameter or larger lengths) have a tendency to shrink the frequency window between resonant and anti-resonant frequencies making it difficult or impossible for ultrasonic generators to lock on to the proper frequency to drive the waveguide, blade and transducer assembly.
Some current designs of clamp coagulator shears utilize elastomer material such as silicone for node supports along the length of the blade. The most distal node support is typically silicone to provide for a seal around the blade. Where higher clamp forces are desired, as is the case with longer active blade lengths, it is desirable to have a rigid distal node support. Many problems, however, are inherent with rigid node supports. Materials such as thermoset polymers that are capable of withstanding the pressure and temperature requirements of an ultrasonic blade node support are often too expensive to be utilized in production. The use of thermoplastics would improve manufacturability from a cost perspective but may not hold up to the pressure and temperature requirements of an ultrasonic blade node support.
Some current designs of clamp coagulator shears utilize a constant force spring mechanism that prevents the application of too much force to the clamp arm and blade. Although the mechanism provides relatively constant force to the system, the spring imparts some slope to the force curve. In applications where the clamp force is low, the slope is not significant. In applications with high clamp forces, however, the difference in force attributable to the slope over the possible range of spring compressions becomes very significant and may exceed the maximum force allowable in the blade, in the tube assemblies or in other components of the system. The high slope could allow the maximum force to be exceeded under abuse modes or through normal manufacturing tolerance variations. If this occurs, the blade may bend, the actuation mechanism may fail or undesirable tissue effects may occur (i.e. fast cutting, but minimal tissue coagulation). This situation is aggravated by the fact that a portion of the jaw (the clamp arm and pad) of the device can meet sufficient resistance to engage the force limiting mechanism when the clamp pad almost contacts the blade (when transecting thin tissue or at the end of the transection or clamping solid objects such as other devices) or when the clamp arm is still open with respect to the blade (when transecting thick tissue).
Some current designs of clamp coagulator shears utilize force-limiting springs to ensure that clamp forces are within a specified range. It is also necessary for the force-limiting spring design to allow the surgeon to “feather” (apply less than the maximum force and slowly increase to the maximum force). In these mechanisms, therefore, the jaw closes until a predetermined force is met and then the additional stroke drives the mechanism into the force limiting range. In some cases, though, the surgeon may, unknowingly, fail to apply the full force of the jaw against the tissue resulting in incomplete tissue cuts or insufficient coagulation. Alternatively, the surgeon may unknowingly open the clamp arm during a transection that results in incomplete tissue cuts or insufficient coagulation.
Some current designs of clamp coagulator shears utilize a foot pedal to energize the surgical instrument. The surgeon operates the foot pedal while simultaneously applying pressure to the handle to press tissue between the jaw and blade to activate a generator that provides energy that is transmitted to the cutting blade for cutting and coagulating tissue. Key drawbacks with this type of instrument activation include the loss of surgeon focus on the surgical field while the surgeon searches for the foot pedal, the foot pedal gets in the way of the surgeon's movement during a procedure and surgeon leg fatigue during long cases.
Some current designs of torque wrenches for ultrasonic surgical instruments utilize a multi-piece torque wrench for use in properly torqueing an instrument to an ultrasonic handpiece. A multi-piece assembly is more costly in that separate pieces have to be molded and then assembled. In addition, the pieces have a tendency to wear rapidly leading to failure of the wrench.
It would be desirable to provide an ultrasonic surgical instrument that overcomes some of the deficiencies of current instruments. The ultrasonic surgical instrument described herein overcomes those deficiencies.